Use two ATX powersupplys
for additional power.
This tutorial will show you how to use two
standard
ATX-12V power supplies in your computer to deliver extra power. The author
(John Zitterkopf) used this design to power a Dual Xeon, Geforce 6800 GT, and
many other peripherals. First some ground rules:
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ALL RIGHTS RESERVED! This design may not be used or
sold by any entity without prior written consent from the author!
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Use this tutorial at your own risk. While the author's
computer is configured this way; it is not to spec and may have long
term repercussions. The author cannot be held responsible for misuse or
damage resulting from this tutorials use.
Applying this modification WILL VOID your warranty for the
master PSU.
-
This tutorial is Copyright 2004 by John Zitterkopf. Linking
to this WWW page is permitted; but reproduction in any form is not permitted
without written permission. Do not link directly to the GIF image. Instead
link to this page. You may print this tutorial/GIF for *personal*
use / reference; but do not reproduce it.
-
This tutorial is made possible from the generous support of
our customers. Please consider purchasing
some memory from us or purchase
some software developed by our company.
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This tutorial uses two ATX PSUs. One configured as a Master.
The other configured as an Auxiliary. The Master PSU drives the Motherboard;
while the Slave PSU drives various peripherals.
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This tutorial requires a master ATX PSU with AUX
connector. The AUX connector is usually reserved for early Server
boards. It is 6pin "inline" connector which looks like an old
AT style connector. This connector is used for return grounds between
master and slave PSUs. The AUX connector is pictured in this
document.
[For the record; the Author's Master PSU is an Antec EPS-12V 550W PSU.]
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The Auxiliary PSU has no special requirements other than
being ATX complaint.
[For the record; the Author's Aux PSU is an Antec 330W ATX PSU.]
Now that the ground rules have been set; lets get to work.
The idea of this design is not based upon any relay type designs
currently on the market / Web. The circuit in question uses ATX standard signals to
properly power up both PSUs before the Power OK (PWOK) signal is sent to the
motherboard. This allows both PSUs to be supplying the correct voltage to all
components before the system is allow to begin POST.
This design was created using free version of Eagle
PCB. The
circuit boards were home etched using the Gootee
Laser Printer transfer method. This entire design was done at home; only
a trip to a local parts supplier to get a few parts was necessary. I used the
Staples "picture paper" and Ammonium Persulfate as an enchant. Etching
was done in a 1gallon plastic aquarium with a water pump to agitate the enchant. This
is a Double Sided PCB.
Schematic
Without any further delay; here's the schematic of this circuit:
Figure 1. Master/Auxiliary PSU
schematic
(Click image to enlarge)
Parts list:
Part Value Device Package Library Sheet
----------------------------------------------------------------------
IC1 74LS12N 74LS12N DIL14 74xx-us 1
JATX_A ATX_POWER ATX_POWER ATXPOWER atxpower 1
JAUX_M AUX_PS1 MOLEX8619 atxpower 1
JM 22-23-2041 22-23-2041 con-molex 1
LEDA RED LEDCHIPLED_1206 CHIPLED_1206 led 1
LEDM RED LEDCHIPLED_1206 CHIPLED_1206 led 1
LEDO ORANGE LEDCHIPLED_1206 CHIPLED_1206 led 1
Either through hole:
RA 1K R-US_R0603 R0603 rcl 1
RM 1K R-US_R0603 R0603 rcl 1
RO 1k R-US_R0603 R0603 rcl 1
or surface mount resistors can be used:
RAA 1K R-US_0207/10 0207/10 rcl 1
RMA 1K R-US_0207/10 0207/10 rcl 1
ROA 1K R-US_0207/10 0207/10 rcl 1
Optional Components for later expandability
J1 ED555-3 ED555-3 ADS 1
J2 ED555-3 ED555-3 ADS 1
Circuit Operation
This circuit works by tying into the PSON# signal
from the motherboard. When the user presses the power button on the computer's
front panel; the motherboard pulls PSON# to an active low with tells the PSU to
begin ramping it's power rails. Both the Master and the Auxiliary PSU watch the
PSON# signal. PS_ON# is the green wire in the ATX bundle.
Both PSU begin to power up their rails and eventually report that the rails
are in spec by driving PWR_OK high. The circuit works by logically ANDing
the PWR_OK signals from both the Master and the AUX psu. When both report
high; the circuit pulls PWROK_OUT high to signal the motherboard to start it
power up sequence. PWR_OK is the grey wire in the ATX bundle.
JM provides an easy connection point for PS_ON#, PWOK_M, and PWOK_OUT; where:
- PS_ON# is the signal from the motherboard;
- PWOK_M is the PWR_OK signal from the Master PSU;
- PWOK_OUT is the signal back to the motherboard.
In order to minimize the number of connectors on the circuit board; the
author decided to splice into the Master PSU's ATX bundle; rather than two
additional connectors and the associated wiring nightmare associated with those
connectors. A picture detailing this modification can be seen here.
When the Master PSU's rails are in spec; LEDM lights.
When the Aux PSU's rails are in spec; LEDA lights.
When the circuit reports both PSUs are in spec; LEDO lights.
Grounding between the Master, Aux, and peripherals are through COM1,COM2, and
COM3 of the JAUX_M connector. This is the 6pin Auxiliary connector from the
Master PSU. Additional grounding is performed by the metal Chassis which the two
PSUs are mounted. The 3.3 and 5V rails from this connector are No Connects and
are not used by the circuit.
The circuit is powered from the 5Volt standby rail (+5VSB) of the AUX PSU.
J1 and J2 are optional components; and are provided for future MODs which
need 3.3V, 5V,
+12V or -12VDC from the AUX PSU.
Here's the completed Circuit Board:
Figure 2. Dual ATX PSU Control Board.
Installed. With
Lights.
That's about all you need to know. Armed with the information above; you should
be able to power a PC with two PSUs.
Please feel free to leave us comments or improvement suggestions for this
tutorial at no_spam@zittware.com.
While your here; Check out our other tutorials which may be of interest to you.
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